Use c_char in static_symbol.rs to fix jlrs on Linux AArch64 #471

Job	Run time
test-linux (stable, false)	2m 35s
test-linux-lts (stable, false)	1m 34s
test-linux (beta, false)	1m 45s
test-windows-gnu (stable-x86_64-pc-windows-gnu, false)	3m 15s
test-macos (stable, false)	1m 16s
test-windows-gnu (beta-x86_64-pc-windows-gnu, false)	3m 25s
test-linux (nightly, true)	1m 48s
test-macos (beta, false)	1m 19s
test-windows-gnu (nightly-x86_64-pc-windows-gnu, true)	3m 48s
test-windows-gnu-lts (stable-x86_64-pc-windows-gnu, false)	12m 15s
test-macos (nightly, true)	1m 36s
test-windows-msvc (stable-x86_64-pc-windows-msvc, false)	4m 16s
test-windows-msvc-lts (stable-x86_64-pc-windows-msvc, false)	10m 12s
test-windows-msvc (beta-x86_64-pc-windows-msvc, false)	2m 39s
test-windows-msvc (nightly-x86_64-pc-windows-msvc, true)	2m 41s
julia-module-test-macos	41s
docs	25s
julia-module-test-linux	35s
julia-module-test-windows-gnu	1m 53s
	57m 58s

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